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package oracle.toplink.essentials.internal.expressions;
import java.util.*;
import java.io.*;
import oracle.toplink.essentials.exceptions.*;
import oracle.toplink.essentials.mappings.*;
import oracle.toplink.essentials.queryframework.*;
import oracle.toplink.essentials.internal.helper.*;
import oracle.toplink.essentials.expressions.*;
import oracle.toplink.essentials.internal.sessions.AbstractRecord;
import oracle.toplink.essentials.internal.sessions.AbstractSession;
/**
* Field expressions represent a field of a table.
* Their base is either a table or object expression.
* This is used for mapping queries and to allow queries on non-mapped field or tables.
*/
public class FieldExpression extends DataExpression {
protected DatabaseField field;
protected transient DatabaseField aliasedField;
/**
* FieldExpression constructor comment.
*/
public FieldExpression() {
super();
}
/**
* FieldExpression constructor comment.
*/
public FieldExpression(DatabaseField newField) {
super();
field = newField;
}
/**
* FieldExpression constructor comment.
*/
public FieldExpression(DatabaseField newField, Expression myBase) {
super();
field = newField;
baseExpression = myBase;
}
/**
* INTERNAL:
*/
public void clearAliases() {
super.clearAliases();
aliasedField = null;
}
/**
* INTERNAL:
* Used for debug printing.
*/
public String descriptionOfNodeType() {
return "Field";
}
/**
* INTERNAL:
* Return the field appropriately aliased
*/
public DatabaseField getAliasedField() {
if (aliasedField == null) {
initializeAliasedField();
}
return aliasedField;
}
/**
* Return the alias for our table
*/
private DatabaseTable getAliasedTable() {
DataExpression base = (DataExpression)getBaseExpression();
if (!getField().hasTableName()) {
base.getDescriptor().buildField(getField());
}
DatabaseTable alias = base.aliasForTable(getField().getTable());
if (alias == null) {
return getField().getTable();
} else {
return alias;
}
}
/**
* INTERNAL:
* If there are any fields associated with this expression, return them
*/
public DatabaseField getClonedField() {
return (DatabaseField)getField().clone();
}
/**
* INTERNAL:
* If there are any fields associated with this expression, return them
*/
public Vector getClonedFields() {
Vector result = new Vector(1);
result.addElement(getField().clone());
return result;
}
/**
* INTERNAL:
*/
public DatabaseField getField() {
return field;
}
/**
* INTERNAL:
* Return all the fields
*/
public Vector getFields() {
Vector result = new Vector(1);
result.addElement(getField());
return result;
}
/**
* INTERNAL:
* Alias the database field for our current environment
*/
private void initializeAliasedField() {
DatabaseField tempField = (DatabaseField)getField().clone();
DatabaseTable aliasedTable = getAliasedTable();
// Put in a special check here so that if the aliasing does nothing we don't cache the
// result because it's invalid. This saves us from caching premature data if e.g. debugging
// causes us to print too early"
// if (aliasedTable.equals(getField().getTable())) {
// return;
// } else {
aliasedField = tempField;
aliasedField.setTable(aliasedTable);
// }
}
/**
* INTERNAL:
*/
public boolean isAttribute() {
return true;
}
public boolean isFieldExpression() {
return true;
}
/**
* INTERNAL:
* Print SQL onto the stream, using the ExpressionPrinter for context
*/
public void printSQL(ExpressionSQLPrinter printer) {
printer.printField(getAliasedField());
}
/**
* INTERNAL:
* Print java for project class generation
*/
public void printJava(ExpressionJavaPrinter printer) {
getBaseExpression().printJava(printer);
printer.printString(".getField(\"" + getField().getQualifiedName() + "\")");
}
/**
* INTERNAL:
* This expression is built on a different base than the one we want. Rebuild it and
* return the root of the new tree
*/
public Expression rebuildOn(Expression newBase) {
FieldExpression expression = new FieldExpression(getField(), getBaseExpression().rebuildOn(newBase));
expression.setSelectIfOrderedBy(selectIfOrderedBy());
return expression;
}
/**
* INTERNAL:
* Set the field in the mapping.
*/
public void setField(DatabaseField newField) {
field = newField;
}
/**
* INTERNAL:
* Rebuild myself against the base, with the values of parameters supplied by the context
* expression. This is used for transforming a standalone expression (e.g. the join criteria of a mapping)
* into part of some larger expression. You normally would not call this directly, instead calling twist
* See the comment there for more details"
*/
public Expression twistedForBaseAndContext(Expression newBase, Expression context) {
Expression twistedBase = getBaseExpression().twistedForBaseAndContext(newBase, context);
return twistedBase.getField(getField());
}
/**
* Do any required validation for this node. Throw an exception if it's incorrect.
*/
public void validateNode() {
DataExpression base = (DataExpression)getBaseExpression();
if (getField().getTable().hasName()) {
Vector tables = base.getOwnedTables();
if ((tables != null) && (!tables.contains((getField().getTable())))) {
throw QueryException.invalidTableForFieldInExpression(getField());
}
}
}
/**
* INTERNAL:
* Return the value for in memory comparison.
* This is only valid for valueable expressions.
*/
public Object valueFromObject(Object object, AbstractSession session, AbstractRecord translationRow, InMemoryQueryIndirectionPolicy valueHolderPolicy, boolean isObjectUnregistered) {
// Joins not supported.
if (getBuilder() != getBaseExpression()) {
throw QueryException.cannotConformExpression();
}
// For bug 2780817 get the mapping directly from the object. In EJB 2.0
// inheritance, each child must override mappings defined in an abstract
// class with its own.
DatabaseMapping mapping = session.getDescriptor(object.getClass()).getObjectBuilder().getMappingForField(getField());
if (mapping == null) {
throw QueryException.cannotConformExpression();
}
return mapping.valueFromObject(object, getField(), session);
}
/**
* INTERNAL:
* Used to print a debug form of the expression tree.
*/
public void writeDescriptionOn(BufferedWriter writer) throws IOException {
writer.write(getField().toString());
}
/**
* INTERNAL: called from SQLSelectStatement.writeFieldsFromExpression(...)
*/
public void writeFields(ExpressionSQLPrinter printer, Vector newFields, SQLSelectStatement statement) {
DatabaseField field = getField();
if (field != null) {
newFields.addElement(field);
writeField(printer, field, statement);
}
}
}
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